Ion desorption induced by F 1s region transitions of poly(tetrafluoroethylene)

Abstract

Auger electron photo-ion coincidence (AEPICO) and kinetic energy ( E k) distribution of desorbed ions of poly(tetrafluoroethylene) (PTFE) were observed to study the mechanism of the site-specific ion desorption. From the photon energy dependence of Auger electron spectra at fluorine (F) K-edge region it is found that the spectator-Auger shift at hν = 689.1 eV is about 5 eV. To estimate the contribution of spectator-Auger component to the Auger spectra, the difference Auger spectra were obtained by subtracting the Auger spectrum above F 1s ionization energy from observed Auger spectra. AEPICO yield spectra for F + at hν = 689.1 eV gives a large intensity at E k = 655 eV. The electron kinetic energy position of this intense F + AEPICO peak agrees with that of the difference Auger spectra. The peak position in the E k distribution of desorbed ion by irradiation of photons at hν = 689.1 eV is about 1 eV larger, as compared with those excited with hν = 693 and 722 eV. These results indicate that the most probable mechanism for F + ion desorption induced by the transition from F 1s to σ(C–F)* is the spectator-Auger-stimulated ion desorption with the steep potential curve for C–F bond dissociation.